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Investigation into undesirable incident involving falling BOP on the Transocean Searcher

During transport/lifting of a blow-out preventer (BOP) on the mobile facility Transocean Searcher on 2 June 2007, the connection between the BOP/riser and the lifting device (top drive) failed. The BOP (weighing approx. 200 tonnes) fell approx. 1 metre, ending up standing on the edge of the transport cart. The Petroleum Safety Authority Norway has investigated the incident. The cause of the incident can probably be related to an error made during the fitting of running tools to the riser section.

The Transocean Searcher is assigned the tasks of completion (making ready for production) wells previously drilled at the Åsgard field. The Transocean Searcher received an Acknowledgement of Compliance in December 2003.

The BOP was to be transported to the seabed and then be connected to an X-mas tree in the subsea template. The BOP was to be lifted using risers which were then connected to the rig's top drive with a running tool.

While the BOP was lifted clear of the transport cart which had transported it from storage, and while the transport cart was returning - the running tool dropped the riser and the BOP fell down on the transport cart. It ended up standing askew (approx. 9 degrees), and the two riser joints were askew in the derrick. The weight registered in the top drive was approx. 207 tonnes, including the block, of which the BOP and riser weighed approx. 180 tonnes.

Statements made during the interviews indicate that it was a matter of the transport cart being driven only a few seconds more for the BOP to hit it in a manner that would have caused it to fall into the sea.

The incident caused no personal injuries, but it had the potential to cause a fatal accident under marginally different circumstances.

There was no risk of the BOP hitting seabed installations during a fall.

It is likely that the running tool device was not fitted far enough into the riser before activating the fastener which secured the connection. Control routines as described in the procedure/interpreted into the procedure for fastening running tools to the risers were followed, but did not address this matter.

The mentioned procedure was in reality written for the connection of risers, and was not suited to describing the connection of the running tool device in question. Nor did it provide a description of the risk potential related to the operation.

The running tool used was modified some years ago, and no basic documentation existed for this activity, nor was the equipment tagged.

Contact in the Petroleum Safety Authority Norway:
Finn Carlsen, Director for supervisory activities
Telephone: +47 51 87 60 81